Hello All,

My car is a 1974 260Z that has the original L26 engine with 4 speed tranny.

I recently installed Triple Webers (DCOE40) and headers but can't get the car run well. I have gone through several main jets, chokes, and air jets sizes and am now at this setting:

Main Jet - 120

Air corrector Jet - 180

Idle Jet - 50F9

Choke - 34

Emulsion Tube - F9

The carbs are synched, idling is good, the car runs well in low speed and low gear, lower rpm. I can run up to 80mph with the throttle half open but when I floor it, I hit that dead spot and the car sputters and bogs down.

I installed a higher capacity ignition coil - Red MSD Blaster 2 to give more spark but the car won't even start on this coil. I installed it along with the original resistor.

Does this have something to do with the distributor of the car? I have attached a picture of the distributor - please help me to identify what type of distributor this is.

Do I have the right combination of jets on the carbs?

What am I missing here?

Can't wait to enjoy the Webers/Headers at full power. Please help!

Thank you much.

Is the dead spot consistent at the same RPM in all gears or just at 80 MPH?

Things to consider:

1) Vacuum advance / timing issue.

2) Some form of fuel restriction / pressure insufficiency (fuel filter clogged, weak pump, etc.)

3) Some form of other restriction (head / exhaust / etc.) (this could be a flier).

Try 130 main jets. What is your Pump jet size?

I have exactly the same problem with the triple Dellorto's I have recently installed. I have got the idle (or low revs) mixture right and the high revs mixture right after testing various jets and using a Colortune spark plug.

When you floor the accelerator the Acc Pump Jets squirts fuel into the venturi and this is the fuel to take you through the transition from running on the idle jet to running on the main jet, which occurs around 3000 revs.

If I floor it at anything under 3000 revs it dies and does not recover until I back off the acc a little and if I accelerate on 3/4 throttle I don't have the problem. I cannot decide if it is getting too much or not enough fuel when I floor it.

Any theories?

Warren

Is the dead spot consistent at the same RPM in all gears or just at 80 MPH?

Things to consider:

1) Vacuum advance / timing issue.

2) Some form of fuel restriction / pressure insufficiency (fuel filter clogged, weak pump, etc.)

3) Some form of other restriction (head / exhaust / etc.) (this could be a flier).

The dead spot comes at any speed once I floor it.

1. The timing is advanced to 14 degrees as recommended by Weber. The vacuum hose is not attached to the carb or manifold.

2. Fuyel filter is new. I am using an electric pump and the original mechanical pump in tandem.

I thought it will get solved by installing a high output coil, but it seems that my distributor will not accept a low resistance/high output coil which is why I am asking for help to identify the distributor currently on my car. I don't think it is the original.

Try 130 main jets. What is your Pump jet size?

Curtis,

Thanks, I'll try the bigger main jets.

That's an impressive set up you have. What distributor are you using?

Curtis,

Thanks, I'll try the bigger main jets.

That's an impressive set up you have. What distributor are you using?

Stock 240Z distributor (recurved) with Crane HI-6 ignition and optical trigger.

The most valueable tool for tuning is to use a wideband oxygen gauge. AEM makes a nice one. I bought mine from Summit Racing and mounted in the stock clock housing.

http://store.summitracing.com/partdetail.asp?autofilter=1&part=AVM%2D30%2D4100&N=700+4294925228+4294925227+400407+4294765928+4294906153+4294906151+308464+115&autoview=sku

My 74 has the same distributor with a msd 6a and blaster 2 coil. The original transistor module has been removed.

Des Hammils book on Webers and Dellortos talks about this probelm and he says it can occur if there is not enough fuel in the emulsion tubes when you transition to the main jet. This could be caused by float level adjustment or poor fuel delivery.

Check the float adjustment and also curious as to what size Pump Jets you have

Float adjustment is 15mm droop when fully open and 7.5mm shut off for a Weber.

Warren

Warren,

Pump Jets - 40

Beezee,

Do you mean the same distributor as mine on the photo?

Thank you Curtis!

I'll be tinkering during the long weekend and let you guys know how it goes.

Cheers!

Yes, magnetic pick-up . There,s a casting # D6F3-01 to the right of the vacuum pot